1. Field of the Invention
The present invention relates to an image processing device, a computer-readable storage medium, and an image processing method and particularly relates to an image processing device, a computer-readable storage medium, and an image processing method for processing a fluorescent light image based on the fluorescent light from an object.
2. Description of the Related Art
Endoscopes are used in the medical field to observe the internal organs of a subject. An elongated and flexible insertion unit of an endoscope is inserted into the body cavity of a subject, such as a patient. White light is applied to body tissue in the body cavity via the inserted flexible insertion unit. By receiving the light reflected from the body tissue with an imaging unit in the flexible insertion unit, a white light image of the body tissue is captured. The white light image of the body tissue is displayed on a display unit of the endoscope. A user, such as a doctor, observes the interior of the body cavity of the subject using the white light image of the body tissue that is displayed on the display unit of the endoscope.
In the field of endoscopy, endoscopes have also been used recently that allow fluorescence observation of an observed region, such as body tissue in the body cavity. A fluorescence-observation endoscope applies excitation light to body tissue in the body cavity via a flexible insertion unit that is inserted into the body cavity and captures a fluorescent light image of the body tissue by receiving, with its imaging unit in the flexible insertion unit, light of autofluorescence or drug fluorescence that is generated from the body tissue due to the application of excitation light. The fluorescent light image of the body tissue that is captured as described above is displayed on the display unit of the endoscope and is observed by a user, such as a doctor. There are also apparatuses that acquire a normalization image using light emitted from an observed region, such as body tissue, due to the application of light on the observed region, and that performs division regarding a fluorescent light image of the observed region using the normalization image in order to generate a normalized fluorescent light image (see, Japanese Laid-open Patent Publication No. 2002-336187).
The luminance value of each pixel of the normalization image decreases with an increase (lengthening) in imaging distance between the observed region and the imaging unit and increases with a decrease (shortening) in the imaging distance between the observed region and the imaging unit.